The invention is generally directed to processes for utilizing soy proteins in food products made using emulsions of edible food oils and/or lipids. The present invention is especially directed to utilizing soy proteins in salad dressings and related products.
Emulsions of edible food oils and lipids, water, emulsifiers, and various flavorings are commonly used as various forms of salad dressings and related food condiments or ingredients. Such emulsions also may be used to form whipped food products, spreads, and frozen dessert products. When used as salad dressings, such emulsions may take various forms, including pourable dressings and spoonable dressings. The pourable and spoonable dressings differ in oil/lipid and water content, as well as in the flavorings they contain. Pourable dressings typically have a relatively low oil and/or lipid content and low viscosity so that they can be dispensed in liquid form from a bottle or other container. Spoonable dressings typically have a relatively high oil and/or lipid content and viscosity and are dispensed in a thickened or semi-solid form.
One example of spoonable dressing emulsions are conventional mayonnaise products which are water continuous emulsions, containing not less than 65 percent by weight dispersed oil, based on U.S. FDA Standards of Identity. As naturally constituted, mayonnaise compositions employ egg yolk as an emulsifying agent to disperse the oil phase in the water phase. Mayonnaise products also commonly include other optional ingredients such as salt, sweeteners, spices, vinegar, and other flavor components. The oils in traditional mayonnaise products may be one or more edible vegetable oils such as soybean or safflower oil. Mayonnaise is generally understood to be sufficiently viscous as to be semi-solid and non-pourable.
A conventional mayonnaise generally may be prepared by combining ingredients such as those described above and premixing them. The resulting premix is transferred to an emulsifying apparatus which provides high shear rates, such as a colloid mill or a high pressure homogenizer. The high shear rate disperses the oil, with the effect of the emulsifying agent, into finely divided droplets to produce the oil-in-water emulsion. The high density of droplets contributes to the high viscosity and high yield strength of the resulting mayonnaise.
Other similar spoonable dressing include oil-in-water emulsions with less than 65 percent oil which are prepared using starches or other similar ingredients to stabilize the emulsified system. According to the U.S. FDA Standards of Identity, such salad dressing must contain at least about 30 percent vegetable oil and about 4 percent liquid egg yolk (or its equivalent).
Many other emulsion dressing products are known to employ lower levels of oil; still others have been developed in which little or no oil is found. Products with lower, yet still significant levels of oil utilize alternative emulsifying agents, bulking agents, fillers, and/or thickeners to assist in providing a stable emulsion system. In such compositions, as with other similar edible emulsions systems, it is considered a desirable and important characteristic to provide organoleptic properties, such as mouthfeel, viscosity, density, flavor profiles, and the like that are similar to mayonnaise type emulsions.
Mayonnaise products and other salad dressings with large amounts of oil and utilizing significant amounts of eggs as emulsifiers are often considered undesirable from a dietary aspect. The high level of oils and the presence of eggs provide a relatively high caloric content in the form of fats, and a source of undesirable amounts of cholesterol. Therefore, considerable effort have been devoted to developing salad dressings with reduced fat and cholesterol levels. Moreover, considerable efforts have also been devoted to preparing foods food ingredients that provide positive health benefits.
The health benefits of soybean proteins have been known for some time. These proteins provide good nutritional value and tend to lower blood cholesterol levels in humans. Soybean proteins, in addition, have recently been linked with a possible role in inhibiting cancerous tumor cells. Thus, efforts have been made to incorporate soy protein into a wide variety of different food products in view of those advantages. Moreover, the use of soybean proteins can provide effective emulsifiers, substitute fillers, and bulking agents that are relatively inexpensive and readily available.
It is typically difficult, however, to incorporate significant levels of soy protein into salad dressing products. Even with high pressure homogenization techniques, the direct addition of significant levels of soy proteins to emulsion products (e.g., salad dressings) can result in commercially unacceptable defects relating to texture and flavor. For example, the direct addition of significant levels of soy proteins into salad dressing products often results in gritty and grainy texture as well undesirable soybean flavor. Examples of efforts to utilize soy proteins in salad dressings include U.S. Pat. No. 4,163,808 (use of soy proteins as the sole or dominant emulsifier); U.S. Pat. No. 4,304,795 (use of soybean protein in a semisolid egg yolk-free dressing); and U.S. Pat. No. 4,426,395 (use of a partial hydrolyzate of alcohol denatured soybean protein as an emulsifier).
The invention provides a process for pre-treating soy proteins so that they can be more effectively incorporated in salad dressing products. As a result, the invention provides a low cost, effective ingredient in salad dressing products that is not only believed to be healthy to consume, but also permits a reduction in the amounts of oils and similar high fat, high calorie ingredients in salad dressings and related edible oil emulsions products. Moreover, the invention provides a soy protein with improved properties suitable for use in salad dressings and related products. Such improved properties include, for example, emulsifying, water holding, and fat binding characteristics.
The invention generally relates to a process for incorporating pre-treated soy protein products into emulsions of edible oils, such as, but not limited to, pourable and spoonable salad dressings. The invention may also be used for other related edible or emulsion products such as whipped desserts, spreads, frozen desserts, and the like.
The process comprises pre-treating a soy protein isolate with one or more protease enzymes in an enzymatic hydrolysis step to prepare a partial digest of the soy protein. The hydrolysis step is carried out using an effective amount of protease enzymes selected for their effectiveness in hydrolyzing the soy proteins, and for the flavor profile provided in the final end product using the partially digested protein. The soy protein is hydrolyzed for an amount of time and a temperature effective to partially digest the soy protein isolate without developing adverse flavor characteristics in the partially digested isolate. Typically, the degree of hydrolysis of the soy proteins is about 3 to about 30 percent, and more preferably, about 5 to about 15 percent. For purposes of this invention, the degree of hydrolysis can be determined using the method of Adler-Nissen (xe2x80x9cEnzymatic hydrolysis of proteins for increased solubility,xe2x80x9d J. Agric. Food Chem. 24: 1090-1096 (1976)), which is hereby incorporated by reference.
The partially digested soy protein is then heated to a temperature sufficient to inactivate the protease enzymes. This step also may be utilized to inactivate or kill of any bacteria or other microorganism contamination of the protein digest mixture (e.g., a pasteurization step). The soy protein digest mixture may be used to directly prepare an edible oil/lipid and water emulsion, such as a salad dressing, or may be stored for preparing such products at a later time. When used to prepare salad dressing or edible oil emulsions, the soy protein digest is blended with oil or other lipid phase ingredients and with the water phase ingredients. During this blending step, the soy protein digest should be relatively uniformly dispersed through out the mixture.
The blended mixture is then homogenized or otherwise subjected to shear forces sufficient to disperse the oil/lipid phase in the water phase to form the desired emulsion. The resulting emulsions will include a first phase of edible oils and/or lipids, as well as any other hydrophobic components, dispersed through the second phase of water and hydrophilic components. In an important aspect of the invention, the viscosity of the soy protein containing emulsion typically will be comparable to similar conventional salad dressing emulsion products, and greater than comparable products made using unhydrolyzed soy proteins both immediately after the emulsification step as well as after about 24 hours storage under refrigeration conditions.
In another important aspect of the invention, the organoleptic properties of the soy protein containing emulsions of the invention further demonstrate texture and/or mouthfeel similar to conventional emulsions having a similar formula (except for the soy protein). Moreover, the present soy protein-containing emulsions have a substantially reduced bean-like flavor; indeed, in many cases, such bean-like flavor is not detectable.
In another aspect of the invention, the soy protein isolates are hydrolyzed using from about 0.02 to about 2.0 percent of the protease enzymes at a temperature of about 70 to about 150xc2x0 F. for about 10 to about 300 minutes. In one aspect of the invention, the soy protein is hydrolyzed until the degree of hydrolysis of the soy proteins is about 3 to about 30 percent, and more preferably, about 5 to about 15 percent.
The protein digest is then heated to a temperature of about 160 to about 195xc2x0 F. to inactivate the enzymes. The digested protein then is blended with an oil and other lipid phase, a water phase and additional sweeteners, flavorings, vinegar and other ingredients typical of a spoonable salad dressing. The blended mixture is then homogenized to form a relatively dense emulsion by dispersing the oil and/or lipid phase in fine droplets throughout the water phase to provide a viscosity to the mixture sufficient for use as a salad dressing. Typically, the particles size of this emulsion is about 0.5 to about 10 microns.
Thus, the process of the invention provides edible oil and/or lipid emulsion systems utilizing the dietary, health, emulsification, bulking, and other benefits of soy protein, but without the detrimental effects encountered when unhydrolyzed soy protein isolates are used in similar emulsions. The invention further provides a salad dressing in one aspect with a flavor profile, organoleptic characteristics, and viscosities at the time of preparation and after storage that is comparable to conventional spoonable salad dressings. Moreover, in some applications, the digested soy protein may provide improved emulsifying, water and fat binding, and holding properties.